Replace hand-written loop with str.matches() call.
Replace hand-written loop with str.matches() call.

This should fix #4.

zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools,zsiciarz/rust-ffi-stringtools